DE3933308A1 - HIGH RESOLUTION SCAN AND REPEAT PROJECTION LITHOGRAPHY SYSTEM - Google Patents

Description

The invention is concerned with lithography systems for Illustration of patterns, and in particular the Invention on a lithography process and -device which is a scan and repeat system have, which is characterized in that by cont beard scans complementary edge illuminations for Generate accurate images with high pattern resolution fortune from a mask on a substrate with a generated at high speed and across an image field be that much larger than the maximum image field size of the imaging optics is.

Lithography systems become extensive in manufacturing of integrated circuit chips and electronic Circuit boards used. Such systems include typically a primary exposure source, such as a lamp with a high luminosity or a laser or a source with a different radiation, mask and Substrate positioning devices, a projection system,  to illuminate the pattern on the mask and image on the substrate, and a control device. In particular, it is intended to use a wafer with a Layer of a radiation sensitive material is provided to illuminate or expose to the ge wanted to create circuit patterns that later became metal or otherwise during the further processing is activated. The out lighting can be by means of ultraviolet light or visibility light or other radiation, such as X-rays radiation or electron radiation. It should the target areas are selectively illuminated in such a way as to to activate a special pattern. Integrated scarf Tungsten chips are typically used for many illuminations steps and physical treatment steps during subjected to manufacture.

As the need for chips increasingly increases greater memory and processing capacity increases who the individual bits on the chips with regard to their Dimensions getting smaller. This makes it necessary that the lithographic system used to image this Pattern is used, an ever higher resolution should have liked. At the same time, the larger physika The dimensions of the chips require that one a higher resolution over a larger image field achieved.

One prior art proposal to achieve high resolution is to use optical imaging reduction systems in which the pattern on the mask is reduced by a factor of 5 to 10 when reproduced on the wafer. Since such a reduction system is capable of providing a high resolution only over a limited image field, the exposure area is limited to a chip size, for example an area of 1 cm ² . The entire wafer is processed by exposing one chip, switching to the next chip in one step and repeating the processing. In these conventional systems, known as stepping or repetition systems, the marginal performance is determined by the miniaturization projecting lens assembly, which typically includes a plurality of individual lens elements. As the requirements for resolution increase, the design of these lenses is becoming more and more complicated. Furthermore, when a lens is designed for higher resolution, its field size typically decreases. Designing and providing a lens with both a higher resolution and a larger image field size is an extremely difficult task.

Another proposal in the prior art is an imaging system with a 1: 1 magnification ratio use, in which the wafers through a long and narrow, curved slit is exposed and in which the imaging over the entire wafer takes place in that the entire wafer once over this long and narrow Slot is scanned. Although such systems the Had the ability to expose large chips, they are gone visibly their resolving power due to their small size limited numerical aperture. Furthermore, since device on solution demands now in the range below µm decrease and, for example, in particular to 0.5 µm and less, these scanning systems have additional Difficulties in having masks with the same high resolution like the products to be produced nisse are required. Therefore, these systems have none large entrance in the manufacture of integrated scarf tung chips with dimensions below 1 µm found.  

There are also the to achieve a large image field Possibility to use an imaging system that as Wynne-Dyson interpretation is known and this is an enlargement ratio of 1: 1. Although these systems are great Chips can expose because their enlargement ratio nis 1: 1, they are with the above Disadvantages, especially their resolution assets is severely limited, what is on it is due to the fact that the requirements for the mask too lead to ever greater difficulties.

There are proposals in the field of lithography, one To use electron beam illumination in which either which is a focused electron beam with a bit-around Bit serial write method or a shadow project tion through 1: 1 matrix mask. These systems each have the disadvantages of low exposure speed, and it's complicated and difficult Apply mask technologies. Usual x-ray Lithography systems similarly set the tone print through 1: 1 membrane masks, and have them therefore rarely according to the above Disadvantages with regard to the 1: 1 pattern and the difficulty with regard to the requirements of the masks manufacturing.

Taking into account the restrictions on the previous There is a great deal in common systems discussed Need to provide a lithographic system which has a higher resolution, high exposure speeds and a greatly expanded field size provides.

The invention aims to be a lithography system to sit, which is both a high resolution also a large effective field size as well as a large one  Throughput in manufacturing allows to get accurate Images with a high-resolution mask on a substrate, like a semiconductor wafer.

According to the invention, a device is specified for this purpose, which are referred to as "scan and repeat" devices is going to take an image of the mask over a certain field generate, then over the substrate and the mask at the same time to scan the above field, then the To move the substrate in the transverse direction so that one exposed or exposed new scanning area and then the Sampling is repeated several times to cover the entire sub to expose strat.

According to a further feature according to the invention, a hexagonal image field provided, and the scan takes place via this hexagonal field.

According to another feature of the invention complementary exposures in an overlapping area provided between adjacent scans such that an edge characteristic of a differently exposed Substrate area between the scans completely is missing and that the illumination exposure dose over the entire substrate is even.

According to a further feature according to the invention, a Means for periodically resetting the mask indicated that the mask a variety of chip fields can contain and yet no unacceptable large Has dimensions.

According to another feature of the invention is a back guidance control device for incremental scanning of the Substrate with a constant exposure dose and with a precise position control is provided to the  frequent, repeated realignment of the substrate to the Mask to a large extent at the desired intervals facilitate.

One of the advantages of the invention is that high speed in connection with the Ver may achieve a high resolution over to achieve an image field that is considerably larger than the undistorted field size of the optical image direction is so that you can manufacture integrated Circuit chips with considerably larger dimensions and can enable a higher throughput.

Further details, features and advantages of the invention emerge from the description below of before preferred embodiments with reference to the beige added drawing. It shows:

Regulatory Fig. 1 is a schematic view of a sample-and-repeat lithography system for illustrating an illumination system, a mask which is contained on a mask support, a Projektionslinsenan, a substrate is held by means of a substrate carrier, and a control system,

Fig. 2 is a diagram showing the effective circular and square image field size of the projection lens, the hexagonal illumination region on the substrate and the effective scanning width,

Fig. 3 is a schematic view for Verdeutli monitoring the sample and Wiederholungsein direction, wherein two adjacent Abtastun gene and complementary exposure in the overlapping area between the two hexagonal Ausleuchtbereichen shows ge are thereby clearing transition borderless Be generated between the two samples,

Fig. 4 shows a schematic representation of rimless, overlapping Sechseckabtastung,

Fig. 5 is a diagram of a preferred embodiment of the scanning and repeating device, wherein a scanning device is shown, which changes between left to right and right to left in each fol lowing scan and the substrate movement is shown with w at the end of each scan ,

Fig. 6 is a schematic diagram of the setup plan Ver deutlichung the chip pads on the mask,

A view showing the chip of the mask carrier is Fig. 7 fields on the substrate, wherein the locations are shown at which a resetting as,

Fig. 8 is a view showing by re presentative mask layout plans in conjunction with an adjacent the representation of the mask chip pads and the hexagonal scanning fields, which allow complementary exposure in the overlapping region between adjacent samples and the generation prevent a hem or edge,

Fig. 8A legungsplanes a detailed view of Maskenaus, of m full chip includes fields 2,

FIG. 8B design plan a detailed view of a mask, the 3 m full chip pads comprising

FIG. 8C is a detailed view for Verdeutli monitoring a mask layout plan which m and m full chip part comprises fields,

Fig. 8D is a detailed view of a legungsplanes Maskenaus, the full m and 2 m partial chip pads comprising

Fig. 9 is a schematic diagram of the principle of deutlichung Ver gleichzei term, two-dimensional scanning for a lithography with a high resolving power may,

Fig. 10 is a table showing various exposure parameters including the energy per pulse on the wafer and laser energy for different photosensitivity and laser pulse repetition rates, and

Fig. 11 is a table conditions across the wafer throughput values for wafers with different diameters and different Ausrichtbe.

The invention enables a lithography system to be prepared deliver that has all of the following: (a) It has a high generation resolution images of a mask pattern on a substrate; (b) it has a large effective field of view; and (c) it has one large throughput during processing for exposure of the substrates. The device to achieve this Eigen shaft comprises a substrate carrier, which scan and can move in the transverse direction, a mask wearer who can scan and reset, and the is functionally coupled to the substrate carrier Compensation system, a projection lens arrangement and one Control device.

Fig. 1 shows the essential parts of the device. The substrate 10 , such as a semiconductor wafer, which is coated with a layer of a photosensitive material, is rigidly fixed in the substrate carrier 12 . The mask 14 , which contains a pattern with a high resolution, which is to be imaged on the substrate 10 , is rigidly fixed in the mask carrier 16 . The substrate carrier 12 and the mask carrier 16 can perform extremely fine precision movements, the details of which are briefly explained below. The mask 14 is illuminated by radiation from the illumination system 18 , which comprises a light source 20 , relay lenses 22 and a beam steering device 24 , such as a 45 ° front surface mirror. The illumination source 20 is designed and laid out that its effective radiation level 21 has the shape of a regular hexagon. The relay lens 22 collects the radiation in a certain numerical aperture N A _S from the hexagonal, effective source plane 21 and takes an image with a certain magnification and the numerical aperture NA _ms on the mask 14 . The projection lens arrangement 26 , which comprises a plurality of separate lens elements 28 , forms an accurate image of the pattern with high resolution in the hexagonally illuminated area on the mask with a certain reduction ratio M on the substrate 10 . The projection lens arrangement 26 has a numerical aperture N A _m on the mask side and NA _w on the substrate side. NA _W is determined by the resolution requirements of the lithographic system, and NA _m is related to NA _W by the equation NA _m = NA _W / M. The projection lens arrangement 26 is designed for the largest possible circular image field (see 31 in FIG. 2), and the exposure area on the substrate is then defined as the largest regular hexagon (designated 32 in FIG. 2), which in FIG the circle field specified above can be inscribed.

With reference to FIG. 1, the substrate carrier 12 now scans the substrate 10 over the hexagonal-shaped exposure area, and at the same time the mask carrier 16 scans the mask 14 over the hexagonal-shaped, illuminated area, so that the length of the substrate in the direction of the Scanning is detected. During such scanning, the mask carrier 16 resets the mask several times in its starting position. Upon completion of a scan across the substrate length, the substrate controller 5 moves the substrate 10 in a direction perpendicular to the scan direction and by an amount which will be referred to as "effective scan width" hereinafter. Following such vertical movement of the substrate, a new scan is carried out by precisely moving the substrate and mask carriers in the same way as described above. The effective scan width and the illumination source system have such characteristics that, in combination, they produce a transition from one scan to the next adjacent scan that is completely borderless and free of any intensity unevenness. This aforementioned exposure process, which is carried out by means of a "scanning and repetition" device, is repeated until the entire substrate is exposed with the desired number of patterns. The details of the scan, stepping, resetting, and repetitive motion that were given before are described below. The control device 30 is functionally linked to the illumination system 18 , the mask carrier 16 , the projection lens arrangement 28 and the substrate carrier 12 , and it ensures that the mask and substrate carriers are suitably aligned with the projection lens arrangement so that the mask and substrate carriers perform the scan and repeat movements with the desired synchronization and that the illumination system keeps the desired illumination characteristics constant over the exposure of the entire substrate.

With reference to Fig. 3, the establishment of the hexagonal scan with borderless overlap will now be described. The regular hexagon 36 , which is also designated abghhc , represents the illuminated area on the substrate at any given time. The substrate is scanned from right to left across this illumination area. It is important to point out that the illumination radiation ( 29 in FIG. 1) is itself stationary, as is also the case with the projection lens arrangement ( 26 in FIG. 1). For the purpose of a pictorial representation, the movement of the substrate across the beam can thus be effectively viewed as the scanning of the hexagonal illumination area over a stationary substrate from left to right. This is shown as scan 1 or 37 in Fig. 3 ge. The orientation of the hexagon 36 is such that one of the sides, for example bg , is perpendicular or orthogonal to the scanning direction.

In order to generate the next scan, the substrate is first moved in a direction perpendicular to the scan direction, at a distance w , which is determined by the following equation

w = 1.5 l _h ,

where l _{h is} the length of each side of the hexagon. (Later it will be shown that w is the effective scanning width.) This new position of the illumination area relative to the substrate is denoted by 38 and also represented by denmkf . The scan 2 , designated 39 , is now generated by scanning the substrate across the hexagonal illumination area 38 in a manner consistent with that when the scan 1 was generated.

An essential aspect of the scanning and repetition device described here, in particular the borderless overlap area between adjacent scans, is described in more detail below. First, the non-overlapping areas are specified. In scan 1 , the area swept by the square section bghc of hexagon 36 is not such that it overlaps any part of scan 2 . Similarly, in scan 2, the area swept by the quadrilateral part efkn of hexagon 38 is not overlapping with all parts of scan 1 . However, the area covered by the triangular segment abc of the hexagon 36 in the scan 1 is again swept by the triangular segment def of the hexagon 38 in scan 2 . The cumulative exposure dose which is obtained in the overlapping area and which is equal to that in the non-overlapping area will now be clarified, and it will also be made clear that the transition from scan 1 to scan 2 is borderless in terms of exposure dose uniformity or is seamless.

In FIG. 4 a segment of the hexagon 36 in the form of a strip 40 to the length l ₀ (cm) and the width δ (cm) as viewed in the non-overlapping scan range of the substrate now. Assuming that I ₀ (mW / cm ² ) is the intensity of the incident beam, v _x (cm / s) is the scanning speed and t ₀ (s) is the time of the substrate within which it travels a path l ₀ this results in t ₀ = l ₀ / v _x . The exposure dose D ₀ (mJ / cm ² ), which is taken up by the substrate in the strip 40 , then results from the following equation.

D ₀ = I ₀ t ₀ = I ₀ l ₀ / v _x = I ₀ l _h / v _x .

Now a strip 42 is again considered with a width and parallel to the scanning direction at a distance y from bc or 1 _h / 2- y from the tip a . The length of the strip 42 is given by

l _{y 1} = 2 (l _h / 2- y),

and the time it takes the substrate to scan a length l _h is as follows:

t ₁ = l _{y 1} / v _x = 2 (l _h / 2- y) / v _x .

The dose which is scanned in the substrate region by means of the strip 42 thus amounts to

D ₁ = I ₀ t ₁ = 2 (l _h / 2- y) I₀ / v _x .

Now the scanning by means of the hexagon 38 should be considered. The segment of the hexagon 38 that scans an area that overlaps the area that is scanned by the stripe 42 is the stripe 44 and has a width δ and a length

l _{y 2} = 2 y.

The sampling time for the length l _{y 2} amounts to

t ₂ = l _{y 2} / v _x = 2 y / v _x ,

and therefore the dose taken up in the substrate area scanned by the strip 44 amounts to

D ₂ = I ₀ t ₂ = 2 yI ₀ / v _x .

Thus, the cumulative dose is in the overlap area on

D = D ₁ + D ₂ = 2 ( l _h / 2- y) I ₀ / v _x + 2 yI ₀ / v _x ,
or
D = l _h I ₀ / v _x = D ₀.

Thus, the total exposure dose received at each location in the overlapping areas of the substrate is the same as the dose received in the non-overlapping areas. Furthermore, the entire exposure is seamless, because (a) the dose values obtained by the hexagons 36 and 38 decrease in opposite directions in the overlapping area, and (b) the dose values at the tip (a) and the tip (b) go to zero each time.

From the discussion above it follows that despite the fact that the exposure coverage of the substrate is free from any interruptions, there is a definable parameter of an effective scan width, w , in the sense that the total width (in the direction orthogonal to the scan direction) of the substrate which is exposed by means of N scans amounts to Nw .

The scanning and repeating device, which has been described in the preceding paragraphs, has such a design that all scans take place in the same direction. Thus, with each scan the substrate moves from right to left, at the end of each scan it returns to the starting position, is moved a distance w in a direction perpendicular to the scan direction and then again moves from right to left for the next scan. In the preferred embodiment shown in Fig. 5, the scanning direction is selected to alternate between right to left and left to right on each successive scan and that the w movement in the orthogonal direction occurs at the end of each scan without the substrate returns to the starting position of the immediately ended scan. Thus, scan 1 ( 50 ) proceeds from left to right, and at the end of it the substrate is moved a distance w ( 52 ). Then the scanning 2 ( 54 ) takes place from right to left, and at the end of the same the substrate is again moved by a distance w ( 56 ). Then the scanning 3 ( 58 ) takes place from left to right, etc. All other details of the device according to FIG. 5 correspond to those according to FIG. 3.

The movement of the mask will now be described. Since the projection lens has a reduction ratio M , the patterns on the mask are M times larger than those to be imaged on the substrate. If the substrate is a semiconductor wafer on which integrated circuit chips are to be produced, then each chip field on the mask is M times larger than the chip to be produced on the substrate. Furthermore, since the substrate scans across the stationary illumination beam, the mask is scanned at the same time at a speed M times that of the substrate. However, if the mask scan continued uninterrupted along the entire length of the substrate scan, the mask would have to be of a considerably large size. For example, for a semiconductor wafer about 15 cm (6 inches) in diameter and a projection lens with a reduction ratio of 5, the mask would have to be at least 75 cm (about 30 inches) long, which is practically impossible. This difficulty is overcome in the manner described below.

The mask ( 60 in FIG. 6) is of a manageable size (for example 25 cm (10 inches) long) and contains a very small number m ( m = 2, for example) complete chip fields, as is shown at 62 in FIG. 6 is shown. When the scan across these chip fields on the mask is completed, the substrate carrier and the mask carrier are momentarily stopped ( 66, 68 in FIG. 7). Now the mask carrier is reset to the starting position, the simultaneous scanning of the mask and the substrate is resumed (see FIG. 7), and further m chips are mapped. The mask is then reset. This is repeated until the substrate scan has completely grasped the length of the substrate. The substrate alone is now moved by the effective scanning width w in a direction perpendicular to the scanning direction, and the procedure described above is carried out again in the opposite direction during the next scanning. There is no movement in the y direction, ie in the direction perpendicular to the scanning direction, necessary, since according to the above statements, the effective mask scanning width can be created so that it is sufficient to detect the width of a mask chip field. In those cases in which the chip fields are wider than the scanning width and these must be exposed, the mask carrier is designed so that it can move in the y direction.

Now that the essential aspects of the mask movement have been explained, a summary of the m complete chip fields is now to be made. The mask must have additional patterned areas so that due to the required seamless, overlapping scanning, the entire mask area, which is enclosed in the hexagonal mask illumination area, is imaged on the substrate. These additional, patterned areas on the mask can be in the form of m , complete chip fields ( 70 , FIG. 8A), 2 m , complete chip fields ( 72 , FIG. 8B), m partial chip fields ( 74 , FIG. 8C) or 2 m partial chip fields ( 76 , Fig. 8D) can be selected.

Further details of the movements of the mask and substrate carriers will now be explained. In the preferred embodiment, the illumination source device ( 20 in FIG. 1) uses a pulsed radiation source, such as a laser or a lamp. In this case, the scanning by means of the substrate and mask carrier takes place in several step movements, and each step is carried out synchronously with the start of a pulse from the illumination source. The pulse repetition rate (frequency) is assumed to be f (Hz). For a nominal substrate carrier scanning speed of v _x (cm / s), the substrate carrier is then scanned in a plurality of steps, each of which is v _x / f (cm). Of course, the mask support steps are M times larger. When the step movement over the mask chip fields is finished, all movements are stopped, the mask carrier is reset, and the workflow is repeated as described above. Such Einrich device for the movement of the carrier has two main advantages. On the one hand, an exposure uniformity is obtained through the appropriate design of a control device, which ensures that a carrier step only takes place when the source emits a pulse. On the other hand, since the substrate and mask carriers are synchronized step by step, precise alignment is made possible at all desired intervals. Therefore, if the alignment is to be for each chip and the chip length l _{c is} along the scan direction, then the alignment must be done every l _c f / v _x pulses emitted by the source or the steps performed with the carrier. In cases where the illumination source is a continuous light source instead of a pulsed light source, the mask-substrate alignment process is not related to the source and is done independently here.

Finally, an embodiment variant of the embodiment described above is explained. In this embodiment, which is referred to as "two-dimensional, overlapping scanning", the mask and substrate carriers are scanned simultaneously in both the x direction and the y direction. Referring to Fig. 4, the scan in the x direction begins with scan 1 ( 80 ) from left to right, the direction reverses at the end of scan 1 , scan 2 ( 82 ) is from right to left, the scan 3 ( 84 ) again from left to right, the scan 4 ( 86 ) from right to left, etc. The width of each x scan is indicated in FIG. 9 with w be. This is for illustrative purposes only because the footprint is hexagonal and the overlap between samples 1 and 3 (and between samples 2 and 4 ) is seamless, as noted above. w is thus the effective scanning width according to the definition given above. Simultaneously with the scanning in the x direction, the substrate and the mask are scanned continuously in the x direction. The y sample rate is chosen such that during the time it takes for the substrate to complete a left-to-right scan and a right-to-left scan, the substrate in the y direction by the effective scan width w is moved. Therefore, when v _x and v _{y are} each the xy scan speeds of the substrate, l _{x is} the total x scan length, and t _x and t _{y are} the times by the scan lengths l _x and w in x and y directions, respectively to scan, the relationship of t _y = 2 results in t _x , v _y with v _x

v _y / v _x = w / 2 l _x .

The x and y sampling rates of the masks are denoted MV _x and MV _y, respectively, where M is the reduction ratio of the projection lens arrangement, as stated above.

Before an example of the preferred embodiment according to the invention is to be explained, the essential advantages should be summarized. The scanning and repeating device not only enables a high resolution to be achieved, but it also enables exposure to much larger chips than heretofore in high resolution lithographic systems which have been incrementally scanned and which have the same Projection lens arrangement is used. Referring to FIG. 2, a projection lens arrangement will now be considered with a circular field size 31 with a diameter of 21 _h. The largest, square-shaped chip with an aspect ratio of 1: 2 ( 34 in FIG. 2), which can be exposed with such a lens in the lithographic system with stepping circuit of the usual type, has a width of 21 _h sin (tan ^-1 0, 5) = 0.89 l _h . In comparison, the scanning and repetition system described here can expose chips with a width of w = 1.5 l _h without moving the mask in the y direction. If the scanning and repetition device is configured in such a way that mask movement in the y direction is possible, chips with widths as large as the substrate width can be exposed.

In the above description of the preferred Aus a refractive projection subsystem seeks which is a lens arrangement that a more number of individual lens elements. According to age native designs can use some or all of the opti parts in the projection subassembly reflect elements such as dielectric or metallic Mirror, be. Such an alternative embodiment can be an x-ray illumination and an x-ray have projection subsystem that with a certain Object-to-image ratio is designed and that Has x-ray mirror. The scan and again Collection lithography concept with a seamless dose delivery by means of complementary overlap of the hexagonal exposure, as described in the invention, can also in various lithographic approximation systems set, d. H. Systems where the projection base group takes a certain distance and the mask and the substrate are separated and the image pro ejection takes place in the form of a shadow print. At for example, a scanning and repeating system X-ray approximation lithograph system in which the Invention can be used a hexagonal Have an x-ray that is used to shadow-print a mask pattern is used on a substrate. The mask and the substrate is close to each other, and they who the same time with a corresponding overlap between the adjacent samples, as is done after the Invention is taught to be seamless and even To generate exposure of the substrate. In a similar way can be a lithographic system with electron beam using proximity printing the scanning and  Use repeat details according to the invention if an electron beam with a hexagonal cross cut is provided by the mask and the Substrate can be scanned synchronously and if you have a complementary exposure over the overlapping, gren zenden samples, so that a seamless and the same moderate dose ensured over the entire substrate is. In a similar way, the invention also applies to one lithographic system by means of optical contact or An Proximity contact can be used, whereby the basic concept of Scanning and repetition realized according to the invention light becomes. Finally, the thought of lithography with sampling and repetition in connection with the complementary edge illumination by neighboring Ab touching also with maskless, lithographic systems applicable, where a polygonal beam on the Sub can be focused in two directions is moved to the desired substrate on the substrate to create.

Way of working

The invention performs the method of providing a One-scan and repeat lithography system high resolution, a large field and one high working speed using the following Steps through:

1. It becomes a substrate support for holding the substrate provided which the substrate in one dimension can scan and which in one direction perpendicular can be moved to the scanning direction;

2. A mask holder is provided to hold the mask ben who the mask in the same dimension as the Can scan substrate carrier;  

3. A projection subassembly is specified which has a certain reduction ratio M , which is designed in such a way that the required resolution is obtained, and which has a circular image field size with a diameter which can be smaller than the length of a chip on the substrate which is not smaller than the width of the chip;

4. A lighting subassembly is specified that generates radiation with a wavelength and an intensity that is required by the projection system and that generates a illuminated area on the substrate in the form of a regular hexagon with a side l _h , which in the circular image field can be inscribed;

5. A mask is provided which has a certain number of m of complete, patterned chip fields and additional, patterned fields falling in the hexagonal, illuminated area on the mask;

6. the substrate is scanned across the hexagonal substrate illumination area at a speed v , and at the same time the mask is scanned in a parallel direction across the hexagonal mask illumination area at a speed M v ;

7. The substrate and mask scanning is currently stopped when the exposure of m chips is finished, the mask carrier is reset to its starting position, and the scanning of the substrate and mask carriers is started again;

8. The substrate and mask scanning is stopped at the end of a scanning across the width of the substrate, the substrate is moved by a distance equal to 1.5 l _h in a direction perpendicular to the scanning direction, and the scanning of the substrate and mask carrier in the opposite direction to the directions in steps 6 and 7 are resumed;

9. the substrate and mask carriers are aligned at desired chip intervals during steps 6 to 8 ; and

10. Steps 6 through 9 are repeated until exposure of the entire substrate is complete.

example

An example of an embodiment of a scan and repeat lithography system according to the invention is given below. The hexagonal illumination area on the substrate shown at 32 in FIG. 2 is chosen such that l _h is the length of one side of the effective square field size ( 33 in FIG. 2) of the projection lens arrangement ( 26 in FIG. 1 ) is 10.0 mm. Then l _h , the length of one side of the regular hexagon is 10.0 / mm = 7.07 mm, and the circular image field size ( 31 in FIG. 2) of the projection lens arrangement has a diameter of 2 l _h = 2 × 7.07 mm = 14.1 mm. The projection lens arrangement has a reduction ratio of 5. The illumination area on the mask is a regular hexagon with one side 5 × 7.07 mm = 35.4 mm.

The substrate carrier is designed so that it holds semiconductor wafers with a diameter of 200 m. The substrate carrier scans in the x direction at a speed v = 100 mm / s. The length of each x scan is determined by the segment of the substrate to be scanned and is equal to the substrate diameter (200 mm) for scans at and near the center of the substrate. At the end of the first x scan ( 50 in FIG. 5), the substrate carrier is moved in the y direction by a path equal to the effective scan width w ( 52 in FIG. 5), which is 1.5 l _h = 1, 5 × 7.07 mm = 10.6 mm. After the y movement by w (= 10.6 mm), the substrate is scanned in the negative x direction ( 54 in FIG. 5), and at the end of the same there is a further movement in the y direction of 10.6 mm ( 56 in Fig. 5). Then another x scan ( 58 in FIG. 5) begins in the x direction. This procedure continues until the entire substrate is scanned. Simultaneously with the substrate scanning, the mask carrier scans at a speed of 5 v = 500 mm / s, and its movement is reversed every time the substrate carrier reverses its direction.

In this example, each chip field on the substrate is 10.6 mm wide (same size as the effective scanning width w ) and 22.0 mm long (see FIG. 7). The chip fields on the mask are five times larger, ie 53.0 mm × 110.0 mm. The mask raw body is approximately 125 mm wide and 250 mm long and provided with four complete chip fields as a pattern, which are shown and discussed in FIG. 8A. It should also be noted that the dimensions of a chip field are determined either on the substrate or on the mask in such a way that the cutting gap, ie the distance between neighboring fields, is included.

The mask only scans in the x direction, and its scanning length is the length of the two mask chip fields (220 mm).

After the mask has scanned a length of 220 mm, the mask carrier and the substrate carrier are momentarily stopped, the mask carrier is returned to its starting position (see FIG. 7), and the synchronous scanning of the mask and the substrate is resumed. After two further chip fields have been scanned, the mask carrier is reset again, and the process sequence described above is continued continuously during the exposure of the entire substrate.

The projection lens arrangement is designed in such a way that it works at a wavelength of λ = 248.4 +/- 0.0003 nm. It is a narrow-line and frequency-stabilized krypton fluoride (KrF) excitation laser source. The numerical aperture of the projection lens arrangement on the substrate side is NA _w = 0.46. It is designed in such a way that a resolution value R of 0.35 µm is obtained if the following equation is used.

R = k λ / NA _w

where the value of k = 0.65. With a reduction ratio M = 5, the numerical aperture of the projection lens arrangement is on the mask side (see FIG. 1).

NA _m = M × NA _w = 0.092.

The mask is illuminated in such a way that the partial coherence factor σ = 0.6. The effective numerical aperture of the illumination on the mask thus amounts to

NA _ms = NA _m / σ = 0.153.

The size of the effective source plane ( 21 in FIG. 1) is designed equal to the hexagonal illumination area on the substrate, ie 1 / M the size of the hexagonal illumination area on the mask. Thus the effective numerical aperture of the source, N A _S , is at the source level

NA _S = M × NA _ms = 0.767.

The excitation laser source is operated at a frequency of 204 Hz pulsed. (The choice of 204 Hz for the laser pulse frequency is discussed below in connection with wafer throughput calculation explained.) The scanning of the substrate carrier takes place in steps synchronously with the laser impulses. Consequently moves with each delivery of a laser pulse Substrate carrier by 0.49 mm (this gives an effec tive substrate scanning speed of 100 mm / s). In a similar way Licher way is the mask carrier scanning in the step of 2.45 mm each also with the laser pulses synchronized.

The wafer throughput, ie the number of exposed wafers per hour in such a lithographic system with scanning and repetition, is to be determined below. The hexagonal illumination area on the substrate has a width l _d (for example bc in FIG. 3) given by the following equation:

l _d = l _h = 12.2 mm.

For a substrate scanning speed of v = 10 cm / s, the hexagon width l _{d is} scanned in a time t _d which results as follows:

t _d = l _d / v _x = l _h / v _x = 0.1222 s.

At a laser pulse frequency of f = 204 Hz, the number of pulses emitted during the time that the substrate needs to scan a path l _{d is} as follows:

N = ft _d = l _h f / v _x = 25.

Thus, each point on the wafer picks up the cumulative exposure of N = 25 laser pulses. (It should be clearly emphasized that the laser pulse frequency was chosen to be 204 Hz and not, for example, 200 Hz, in order to achieve that N is an integer.) The laser pulse energy density E _w (mJ / cm ² ) on the wafer be so true that the total exposure dose taken is equal to the sensitivity D _S (mJ / cm ² ) of the photo resist used, and thus amounts to:

D _s = NE _w = l _h fE _w / v _x = 25 E _w ,
or
E _w = D _s / N = D _s v _x / l _h f = D _s / 25.

If, for example, a photoresist with a sensitivity D _S = 50 mJ / cm ^{2 is} used, the laser pulse energy density on the wafer must be E _W = 2 mJ / cm ² . Since the area A of the hexagonal illumination area on the wafer is given by the following

A = l × _{h h} l _h l + 0.5 l × _h = 1.5 _h ² l = 1.3 cm,

the energy per pulse at the wafer e _{w is the} same

e _w = AE _w = 1.5 l _h D _s v _x / f = 2.6 mJ.

Thus p _{w is} the same as the energy impinging on the wafer

p _w = fe _w = 1.5 l _h D _s v _x = 0.53 W.

Assuming an effective transfer efficiency of η = 20% for the complete optical system between the laser and the substrate, the power delivered by the laser amounts to

p _L = p _w / η = 1.5 l _h D _s v _x / η = 2.65 W.

Taking the above equations, various quantitative quantities such as the laser power required and the number of overlap pulses at each point can be determined for all other sets of parameters including resistance sensitivity, scanning speed, pulse repetition rate and the size of the footprint. At a frequency of 303 Hz, for example, if all other parameters are assumed the same as given above, N = 37, E _w = 1.35 mJ / cm ² and e _w = 1.76 mJ, the power of the laser is still p _L = 2.65 W. If a photoresist sensitivity D _S = 10 mJ / cm ^{2 is} used, one obtains at f = 204 Hz, N = 25 according to the previous calculations. Now, however, E _w = 0.4 mJ / cm ² , e _w = 0.52 mJ, p _w = 106 mW and p _L = 0.53 W. A complete set of these results of resistance sensitivities of 10, 50 and 100 mJ / cm ² and laser pulse frequencies of 98, 204 and 303 Hz are given in Table I in FIG. 10.

The total scanning time required to expose the wafers to different sizes results from the following explanations. Since the scanning takes place at a speed of v _x (= 100 mm / s) and the effective scanning width is w (= 1.5 l _h = 10.6 mm), the area effectively exposed per s amounts to

a = wv _x = 1.5 l _h v _x = 10.6 cm².

Thus, a wafer with a diameter d _w , which has an area A _w = π d ² _w / 4, is exposed for a period of time t _e that results with

t _e = A _w / a = π d ² _w / 4 wv _x = π d ² _w / 6 l _h v _x .

The areas of the wafers with a diameter of 125 mm, 150 mm and 200 mm are 122.7 cm², 176.7 cm² and 314.2 cm², respectively. The total exposure times for wafers with a diameter of 125 mm, 150 mm and 200 mm are therefore t _{e , 125} = 11.6 s, t _{e , 150} = 16.7 s and t _{e , 200} = 29.6 s .

The number of chips, n _c , with the width w (= 10.6 mm) and the length l _c (= 22.0 mm) on the wafers with different diameters is obtained by passing the wafer area A _w through the chip area , A _c (= 2.33 cm²) divided. This results in the following:

n _c = A _w / A _c = ( π d ² _w / 4) / w l _c = ( π d ² _w / 4) / 1.5 l _h l _c = π d ² _w / 6 l _h l _c .

For wafers with a diameter of 125 mm, 150 mm and 200 mm, the values for n _c are 52, 75 and 134, respectively.

The wafer throughput is now obtained as described below Wise. One has:

t _e = total exposure time per wafer and
n _c = number of chips per wafer.

The following is also assumed:

t _a = alignment time per alignment process,
n _a , this size indicates that the alignment is carried out once every n _a chip,
t _CH = total scanning time per wafer (including loading, unloading, height adjustment, focusing, other adjustments and stopping) and
W = wafer throughput per hour.

The total time per cycle for a wafer at Editing required by the lithographic machine results from the following:

t _t = t _e + t _OH + t _a n _c / n _a .

The wafer throughput per hour thus amounts to

W = 3600 / t _t = 3600 / ( t _e + t _OH + t _a n _c / n _a )
or
W = 3600 / (π d ² _w / 6 l _h v _x t + _OH + t _a n _c / n _a).

The general expression for wafer throughput given above can be used with any set of values for the parameters l _h , v _x , n _C , t _a , n _a , d _w and T _OH to give a wafer throughput result under the given conditions to determine. For wafers with a diameter d _W = 150 mm, with an alignment that is carried out for every fourth chip (ie n _a = 4) and using l _h = 7.07 mm, v = 100 mm / s, n _c / n _a = 19, t _a = 0.4 s and t _OH = 20 s, the result is W = 81.3 wafers / h. If the alignment is carried out on every tenth chip, one uses n _c / n _a = 8 and obtains W = 90.2 wafers / h. With a side-by-side alignment (ie n _a = 1), W = 54.0 wafers / h. Table II in FIG. 11 shows a complete set of wafer throughput values for wafers with diameters of 125, 150 and 200 mm with three different alignment conditions for each example.

In summary, the invention provides a scan and repeat lithographic system that has high resolution, large effective field size, and high substrate exposure speed. Here, the following is provided: (a) a substrate carrier which can scan a substrate in one dimension and which, if it does not scan in this dimension, can carry out a movement transversely in a direction perpendicular to the scanning direction in such a way that the substrate is positioned for another scan; the substrate carrier exposes the entire substrate by dividing the substrate area into parallel strips and exposing each strip by scanning the length of the strip over a fixed illumination area; (b) a mask carrier can scan in the same direction, in synchronism with the substrate carrier, but at a speed greater than the substrate carrier scanning speed by a certain ratio N ; (c) a footprint subassembly has an effective source plane in the form of a polygon and can evenly light a polygonal area on the mask; (d) a projection subassembly has an object-to-image reduction ratio M that has a polygonal image field with a smaller area than the desired effective image field size of the lithographic system; and (e) complementary exposures are made in an overlapping area between the areas exposed by adjacent scans such that there is no seam in the exposure dose distribution on the substrate between the scans and that the exposure dose delivered to the entire substrate is uniform.

Claims (22)

1. A lithographic system with a high resolution, a high exposure speed, a large effective field size and a scanning and repeating device for generating accurate images of a pattern on a mask on a substrate, characterized by :

• a) a substrate carrier ( 12 ) which can scan a substrate in one dimension, and then, if this dimension is not scanned, can move in the transverse direction in a direction perpendicular to the scanning direction such that the substrate for a further scanning is positioned, the substrate carrier ( 12 ) being able to expose the complete substrate by dividing the substrate surface into a certain number of parallel strips and each of these strips being exposable by scanning the length of the strip over a fixed illumination area,
• b) a load carrier ( 16 ) which can scan in the same dimension and synchronously with the substrate carrier ( 12 ), but at a speed which is the same as the substrate carrier scanning speed multiplied by a certain ratio ( M );
• c) an illumination subassembly ( 18 ) which has the desired characteristics with regard to the wavelength and the intensity distribution, and which has an effective source plane ( 21 ) in the form of a polygon, which enables uniform illumination of a polygonal region on the mask,
• d) a projection subassembly ( 26 ) for imaging the polygonal, illuminated area on the mask onto the substrate, which has an object-to-image reduction ratio ( M ), which has the desired image resolution and has an image field in the form of a polygon and with a surface , which is smaller than the desired effective field size of the lithographic system, and
• e) a control device ( 30 ) which supports the substrate ( 12 ), the mask support ( 16 ) and the light subassembly ( 18 ) with respect to the operation and associates complementary exposures in an overlap area between the adjacent scans ( 1 , 2 , 3 ) exposes areas in such a way that the exposure dose recorded in the overlap area is seamless and that the exposure dose given over the entire substrate is uniform.

2. Lithographic system with scanning and repetition according to claim 1, characterized in that:

• a) the illumination subassembly ( 18 ) has an effective source plane ( 21 ) in the form of a regular hexagon, illuminates an area in the form of a regular hexagon on the mask and the area is oriented in the form of a regular hexagon such that two of the sides are perpendicular to the scan direction,
• b) the projection subassembly ( 26 ) has an image field in the form of a regular hexagon and the regular hexagon is oriented such that two of its sides are perpendicular to the scanning direction, and
• c) the effective width w of each substrate scan defined as the cross separation between the center lines of two adjacent scans is given by:
  w = 1.5 l _h
  where l _{h is} the length of each side of the image field in the form of a regular hexagon on the substrate.

3. A scanning and repetitive lithographic system according to claim 2, characterized in that the effective width w of each substrate scan is equal to the width of each chip on the substrate and that the width of each chip on the substrate is determined as the periodic distance with which the chips on the substrate repeat in the direction perpendicular to the scanning direction. 4. Lithographic system with scanning and repetition according to claim 1, characterized in that:

• a) the direction of substrate movement in each scan is opposite to the direction of substrate movement in an adjacent scan, and
• b) the direction of the mask movement for each scan is opposite to the direction of the mask movement for an adjacent scan.

5. Lithographic system with scanning and repetition according to claim 1, characterized in that:

• a) the number of chip fields on the mask in the scanning direction is equal to a certain number N _m , which is smaller than the number of chips in the longest scan on the substrate, and
• b) the control device ( 30 ) monitors the scanning and, when determining a synchronous scanning by the substrate carrier ( 12 ) and the mask carrier ( 16 ), a sudden pause or a sudden break for each N _m chips for the substrate carrier ( 12 ) Standstill specifies, the mask wearer ( 16 ) is reset in its starting position and for synchronous scanning of the substrate carrier ( 12 ) and the mask wearer ( 16 ) resumes operation.

6. Lithographic system with scanning and repetition according to claim 1, characterized in that the light subassembly ( 18 ) delivers radiation which is pulsed with a certain repetition frequency. 7. Lithographic system with scanning and repetition according to claim 6, characterized in that the ge pulsed radiation emitted by an Exciplex laser becomes.   8. lithographic system with scanning and repetition according to claim 1, characterized in that from the light subassembly ( 18 ) takes an X-ray illumination device of a polygonal area on the mask before. 9. lithographic system with scanning and repetition according to claim 1, characterized in that from the light subassembly ( 18 ) performs an electron beam illumination of a polygonal area on the mask. 10. Lithographic system with scanning and repetition according to claim 6, characterized in that:

• a) the scanning of the substrate carrier ( 12 ) is selected to be a multiple of a certain movement unit of the length of the d _S such that d _s = v _x / f, where v _{x is} the effective substrate scanning speed and f is the pulse repetition frequency of the illumination subassembly ( 18 ) is and
• b) the mask carrier scanning is selected to be a multiple of a movement unit of length d _m , so that the following applies: d _m = Md _S.

11. A scanning and repetitive lithographic system according to claim 10, characterized in that the control means ( 30 ) periodically realigns the mask and the wafers with respect to each other and the interval between successive realignments is determined by the fact that during the interval the The number of pulses emitted by the illumination subassembly ( 18 ) is monitored. 12. A scanning and repeating lithographic system as claimed in claim 11, characterized in that the number of pulses emitted by the illumination subassembly ( 18 ) during the interval between successive realignments is a multiple of l _c f / v _x , where l _{c is} the length of a chip on the substrate in the scanning direction. 13. Lithographic system with scanning and repetition according to claim 1, characterized in that the mask carrier ( 16 ) in addition to its ability to perform a scan, is also movable in a direction perpendicular to the scanning direction. 14. Lithographic system with scanning and repetition according to claim 1, characterized in that:

• a) the object-to-image reduction ratio of the projection sub-assembly ( 26 ) 5 and
• b) the ratio of the mask scanning speed to the substrate scanning speed is 5.

15. Lithographic system with scanning and repetition according to claim 1, characterized in that:

• a) the object-to-image reduction ratio of the projection sub-assembly ( 26 ) is 1 and
• b) the ratio of mask scanning speed to substrate scanning speed is 1.

16. Lithographic system with scanning and repetition according to claim 1, characterized in that the wavelength of the illumination sub-assembly ( 18 ) is in the range of 251 +/- 3 nm. 17. A method for operating a lithographic system with scanning and repetition as well as with a high resolution, a large field and a high operating speed, characterized by the following steps:

• a) providing a substrate carrier for holding the substrate, which can scan the substrate in one dimension and can move transversely thereto in a direction perpendicular to the scanning direction,
• b) providing a mask carrier for holding the mask, which can scan the mask in the same dimension as the substrate carrier,
• c) providing an illumination sub-assembly which has the desired properties with regard to the wavelength and the intensity distribution, which has an effective source plane in the form of a polygon and which can enable uniform illumination of a polygonal region on the mask,
• d) providing a projection subassembly for imaging the polygonal illumination area on the mask onto the substrate, which has an object-to-image reduction ratio M , which has a desired image resolution and which has an image field in the form of a polygon and with an area, which is smaller than the desired effective image field size of the lithographic system,
• e) providing a mask that has a certain number of complete patterned chip fields and additional patterned areas that fall within the hexagonal illuminated area on the mask,
• f) scanning the substrate across the polygonal substrate illumination area at a certain speed v _x and simultaneously scanning the mask in a parallel direction across the polygonal mask illumination area at a speed MV _x ,
• g) stopping the scanning of the substrate and mask carrier with the completion of a scanning over the entire length of the substrate along the scanning direction, moving the substrate a certain distance in one direction to the scanning direction and resuming the scanning of the substrate and mask carrier in Directions that are opposite to the respective directions in step (f),
• h) Providing complementary exposures in an overlap area between the areas exposed by adjacent scans such that an edge or a seam is missing in the exposure dose distribution received on the substrate between the scans and that the exposure dose emitted over the entire substrate is evenly distributed , and
• i) repeating steps (f) to (h) until the exposure of the entire substrate has ended.

18. The method according to claim 17, characterized in that that further the step of aligning the substrate and mask wearers at desired intervals during steps (f) to (i) is provided. 19. The method according to claim 17, characterized in that that further the step is provided according to which the Repeated scanning of the substrate and mask carriers currently at the end of a certain exposure Number of chips stopped less than that Number of chips on the longest substrate scan is, the mask wearer in its starting position is reset and the scanning of the substrate and Mask wearer is resumed. 20. Lithographic system with scanning and repetition as well as with a high resolution, a high exposure speed and a large effective field size, which produces precise images of a pattern present on a mask on a substrate, characterized by:

• a) a substrate carrier ( 12 ) which can scan a substrate in a certain dimension ( x ) and at the same time can scan the substrate in a direction y , which is perpendicular to the direction x , so that the substrate carrier ( 12 ) during the termination a scan in the x direction can simultaneously move in the transverse direction in the y direction and thus position the substrate for a further scan in the x direction, the substrate carrier ( 12 ) thus being able to expose the entire substrate in that the substrate surface is divided into a certain number of strips and each strip is exposed by scanning the length of the strip over a fixed illumination area,
• b) a mask carrier ( 16 ) which can scan in the same two directions and synchronously with the substrate carrier ( 12 ) and at speeds in the x and y directions which are a certain ratio M greater than the corresponding substrate scanning speeds,
• c) an illumination subassembly ( 18 ) which has the desired properties with regard to the wavelength and the intensity distribution, which has an effective source plane ( 21 ) in the form of a hexagon and which permits uniform illumination of a polygonal region on the mask, and
• d) a projection subassembly ( 26 ), which can image the polygonally illuminated area on the mask on the substrate, has an object-to-image reduction ratio M , which has the desired image resolution and has an image field in the form of a polygon and with an area which is smaller than the desired effective image field size of the lithographic system, and
• e) a control device ( 30 ), the substrate carrier ( 12 ), the mask carrier ( 16 ) and from the light subassembly ( 18 ) operationally assigns each other and makes complementary exposures in an overlap area between areas that are exposed by adjacent scans, namely such that the exposure dose distribution taken up in the overlap area is seamless and that the exposure dose given to the entire substrate is uniform.

21. Method for operating a lithographic system with scanning and repetition as well as with a high resolution, a large field and a high operating speed, characterized by the following steps:

• a) providing a substrate regulator for holding the substrate, which can simultaneously scan the substrate in two directions x and y ,
• b) providing a mask holder for holding the mask, which can simultaneously scan the mask in the x and y directions,
• c) providing an illumination sub-assembly which has the desired properties with regard to the wavelength and the intensity distribution, which has an effective source plane in the form of a polygon and which permits uniform illumination of a polygonal region on the mask,
• d) Providing a projection subassembly for imaging the polygonal, illuminated area on the mask on the substrate, which has an object-to-image reduction ratio M , which has a desired imaging resolution and which has an image field in the form of a polygon with a Area which is smaller than the desired effective image field size of the lithographic system,
• e) scanning the substrate simultaneously in x and y directions across the polygonal substrate illumination area with a certain speed in both directions, and at the same time scanning the mask in x and y directions over the polygonal mask removal area at speeds that are the same the corresponding substrate carrier scanning speeds are modified with M ,
• f) stopping the scanning of the substrate and mask carrier upon completion of a scanning over the entire length of the substrate in the x direction, reversing the direction of the scanning in the x direction, and resuming the simultaneous two-dimensional scanning of the substrate and mask carrier as in Steps);
• g) Providing complementary exposures in an overlap area between the areas which are exposed by adjacent, parallel scans such that a seam of the exposure dose distribution recorded on the substrate is missing between the scans and that on the entire exposure dose of substrate is uniform, and
• h) repeating steps (e) to (g) until exposure of the entire substrate is complete.

22. The method according to claim 21, characterized in that further the step is provided according to which the Substrate and mask carrier with a desired one Interval during steps (e) to (h) was sufficient is tested.